1. Technical Field
The present application relates generally to methods and systems for computing data transmission characteristics of network paths.
2. Related Art
The ability to accurately measure network parameters along Internet paths is useful to both Internet Service Providers (ISP) and end users. Internet paths between two hosts may traverse various ISP paths, with each ISP having multiple internal routes and multiple next-hop ISP and/or service level agreement (SLA) choices for the particular source and destination hosts. Therefore, in order to efficiently route data, an ISP must know the network parameters, such as the capacity and available bandwidth, of the different paths that connect the source and destination hosts. End users also find such network parameters useful in order to, for example, select between two mirror sites of a particular host to find the most efficient connection.
In general, a network path between a sender and a receiver will include a number of links (or “hops”) between intermediate hosts, or more specifically, intermediate routers. Each link has a capacity, which is the maximum possible data transmission rate, and an available bandwidth, which is the unused portion of the capacity in the presence other users' data, i.e., cross traffic. The available bandwidth of a link for a particular application depends on a number of factors, including the characteristics of the application itself, the protocols used, and the characteristics of the cross traffic and routers, all of which makes accurate measurement of available bandwidth difficult. Cross traffic varies over time, making available bandwidth even more difficult to measure. A bottleneck link bandwidth may be defined as the available bandwidth of the slowest (i.e., narrowest bandwidth) forwarding element (e.g., router) of the network path. Bottleneck capacity may be defined as the narrowest bandwidth in the absence of cross traffic. Bottleneck bandwidth and capacity are sometimes referred to as “end-to-end” available bandwidth or capacity.